PSI - Issue 5

Dan Mihai Constantinescu et al. / Procedia Structural Integrity 5 (2017) 653–658 Mocian et al./ Structural Integrity Procedia 00 (2017) 000 – 000

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respectively 3.5 m/s in Fig. 3 (b). The previous observations are also explained by the level of penetration produced in the top skin of the sandwich. The PS_PUR panels are severely punctured as shown on the right side of both figures. However, the bottom skin remains totally undamaged at these speeds of impact. At 3.5 m/s the top skin of the panel is completely punctured for PS_PUR and partially punctured for PS_PE. The size of the indentation is also smaller. Thus the PS_PE panel behaves better in impact absorbing more energy.

(a) (b) Fig. 3. (a) Impact of sandwich panels at 2.5 m/s; (b) Impact of sandwich panels at 3.5 m/s.

Impact tests were repeated for two or three sandwich panels at each speed of testing and the reproducibility of the results was very good. The impact speed was afterwards increased to a maximum of 4.5 m/s (133.14 J) and, of course, all phenomena became very complicated. The response of the PS_PE panel is presented in Fig. 4 (a). Top skin is damaged quite severely and bottom skin is slightly indentated, but not damaged. The panel bends a lot along a median plane and the lateral view shows that delaminations are generated in the polystyrene core close to the top skin on opposite sides, as the core is weaker than the AW 106 adhesive. In all, the polystyrene core can absorb the impact energy with a good elastic recovery.

(a)

(b) Fig. 4. Impact of sandwich panels at 4.5 m/s: (a) PS_PE; (b) PS_PUR. Bottom, lateral, and top views.